Intra-cardiac mapping and ablating

ABSTRACT

Systems, methods, and devices allow percutaneous mapping, orientation and/or ablation in bodily cavities or lumens. Such may include a structure that is percutaneously positionable in a cavity, such as an intra-cardiac cavity of a heart. Transducers carried by the structure are responsive to blood flow. For example, the transducers may sense temperature, temperature being related to convective cooling caused by blood flow. A controller discerns positional information or location, based on signals from the transducers. For example, blood flow may be greater and/or faster proximate a port in cardiac tissue than proximate tissue spaced from the port. Position information may allow precise ablation of selected tissue, for example tissue surround a port in the intra-cardiac cavity.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of prior U.S. patent application Ser.No. 13/596,774, filed Aug. 28, 2012, which claims the benefit of U.S.Provisional Patent Application No. 61/532,423, filed Sep. 8, 2011. Theentire disclosure of the applications cited in this paragraph is herebyincorporated herein by reference.

BACKGROUND

1. Technical Field

This disclosure is generally related to surgery, and more particularlyto percutaneously deployed medical devices suitable for determininglocations of cardiac features or ablating regions of cardiac tissue, orboth.

2. Description of the Related Art

Cardiac surgery was initially undertaken using highly invasive openprocedures. A sternotomy, which is a type of incision in the center ofthe chest that separates the sternum, was typically employed to allowaccess to the heart. In the past several decades, more and more cardiacoperations are performed using percutaneous techniques, where access toinner organs or other tissue is gained via a catheter.

Percutaneous surgeries benefit patients by reducing surgery risk,complications and recovery time. However, the use of percutaneoustechnologies also raises some particular challenges. Medical devicesused in percutaneous surgery need to be deployed via catheter systems,which significantly increase the complexity of the device structure. Aswell, doctors do not have direct visual contact with the medical devicesonce they are positioned within the body. Positioning these devicescorrectly and operating the devices successfully can often be verychallenging.

One example of where percutaneous medical techniques have been employedis in the treatment of a heart disorder called atrial fibrillation.Atrial fibrillation is a disorder in which spurious electrical signalscause an irregular heartbeat. Atrial fibrillation has been treated withopen heart methods using a technique known as the “Cox-maze procedure.”During this procedure, physicians create lesions in a specific patternin the left and right atria that block various paths taken by thespurious electrical signals. Such lesions were originally created usingincisions, but are now typically created by ablating the tissue withradio-frequency (RF) energy, microwave energy, laser energy or cryogenictechniques. The procedure is performed with a high success rate underthe direct vision that is provided in open procedures, but is relativelycomplex to perform percutaneously because of the difficulty in creatingthe lesions in the correct locations. Various problems, potentiallyleading to severe adverse results, may occur if the lesions are placedincorrectly.

Key factors which are needed to dramatically improve the percutaneoustreatment of atrial fibrillation are enhanced methods for deployment,positioning, and operation of a treatment device. It is particularlyimportant to know the position of the elements which will be creatingthe lesions relative to cardiac features such as the pulmonary veins andmitral valve. The continuity and transmurality characteristics of thelesion patterns that are formed can impact the ability to block pathstaken within the heart by spurious electrical signals.

Several methods have been previously developed for positioningpercutaneously deployed medical devices within the heart. For example,commonly assigned U.S. Patent Application Publication No. 2008/0004534A1, which is herein incorporated by reference in its entirety, describesvarious intra-cardiac mapping systems based on detecting the portsthrough which blood flows in or out of a heart chamber. Commonlyassigned U.S. Patent Application Publication No. 2009/0131930 A1, whichis herein incorporated by reference in its entirety, describes a devicethat is percutaneously guided to a cavity of a bodily organ (e.g., aheart). The device can discriminate between fluid within the cavity(e.g., blood) and tissue that forms an inner or interior surface of thecavity (e.g., surface tissue) to provide information or mappingindicative of a position, orientation, or both position and orientationof the device in the cavity. Discrimination may be based on flow or someother characteristic, for example electrical permittivity or force. Thedevice can selectively ablate portions of the surface tissue based atleast on the information or the mapping. In some cases, the device maydetect characteristics (e.g., electrical potentials) indicative ofwhether ablation was successful. The device includes a plurality oftransducer elements that are intravascularly or percutaneously guided inan unexpanded configuration and positioned proximate the surface tissuein an expanded configuration. Various expansion mechanisms that includehelical member(s) or inflatable member(s) are described. Other forms ofexpansion mechanisms are described in commonly assigned U.S. ProvisionalPatent Application No. 61/435,213; U.S. Provisional Patent ApplicationNo. 61/485,987; U.S. Provisional Patent Application No. 61/488,639; andU.S. Provisional Patent Application No. 61/515,141 which are each hereinincorporated by reference in their entirety.

Atrial fibrillation is but one example of a cardiac surgery thatrequires effective mapping systems that are percutaneously deliverableto various intra-cardiac cavities. The mapping systems should allow forthe improved determination of the relative position of anatomicalfeatures within the intra-cardiac cavity such as pulmonary veins andmitral valve with respect to a portion of the system that ispercutaneously delivered.

BRIEF SUMMARY

The present design of a medical device with enhanced capabilities fordeployment, positioning and ablating within a bodily cavity such as aheart is disclosed. In particular, the device is configurable from afirst or unexpanded configuration in which a portion of the device issized for delivery to a bodily cavity via a catheter to a second orexpanded configuration in which the portion of the device is expanded toposition various transducer elements proximate a tissue surface withinthe bodily cavity. The device employs a method for distinguishing tissuefrom blood and may be used to deliver superior positional information ofthe device relative to ports in the atrium, such as the pulmonary veinsand mitral valve. The device employs a method for distinguishing tissuefrom blood and may be used to deliver superior positional information ofvarious anatomical features within the bodily cavity. The device mayemploy characteristics such as blood flow detection. The device may alsoimprove ablation positioning and performance by using the same elementsfor discriminating between blood and tissue as are used for ablation.Other advantages will become apparent from the teaching herein to thoseof skill in the art.

A medical system may be summarized as including a structure and aplurality of transducer elements carried by the structure, the structureand the plurality of transducer elements sized to be received within anintra-cardiac cavity, the intra-cardiac cavity defined at least in partby a tissue wall with an interior surface of the tissue wall isinterrupted by one or more ports positioned in fluid communication withthe intra-cardiac cavity. Each transducer element of at least some ofthe plurality of transducer elements is responsive to blood flow toprovide a respective first signal set, each respective first signal setresponsive to blood flow at least proximate a respective one of the atleast some of the plurality of transducer elements. The medical systemincludes a signal source providing a second signal set, a respective atleast one signal within the second signal set provided to each of the atleast some of the plurality of transducer elements. The medical systemincludes a controller communicatively coupled to the transducer elementsand that determines information that specifies a location of each of oneor more regions of the interior surface of the tissue wall and alocation of each of at least one of the one or more ports on theinterior surface of the tissue wall with respect to the one or moreregions based at least in part on a phase of a respective first signalderived at least in part from each respective first signal set, thephase of each respective derived first signal determined relative to aphase of a respective second signal within the second signal setprovided by the signal source.

The second signal set provided by the signal source may consist of asingle signal. The second signal set may include a plurality of signals,each of the plurality of signals having a predetermined phase relativeto a phase of another of the plurality of the signals. The phase of eachrespective derived first signal may be determined relative to a phase ofa same or corresponding signal within the second signal set provided bythe signal source. The phase of each respective derived first signal maybe determined relative to a phase of a single signal within the secondsignal set provided by the signal source. The second signal set mayinclude a plurality of signals, and the phases of each of at least twoof the second signals within the second signal set provided by thesignal source may differ from one another by a predetermined amount.Each respective second signal within the second signal set provided bythe signal source may have a predetermined phase relative to a phase ofthe respective at least one signal within the second signal set providedto the respective transducer element of the at least some of theplurality of transducer elements associated with the respective derivedfirst signal whose phase is determined relative to the phase of therespective second signal.

The medical system may further include at least one synchronousdemodulator that provides the phase of each respective derived firstsignal relative to the phase of the respective second signal within thesecond signal set provided by the signal source. The controller mayperform a frequency domain transform to determine the phase of eachrespective derived first signal relative to the phase of the respectivesecond signal within the second signal set provided by the signalsource. The controller may perform a Fourier transform to determine thephase of each respective derived first signal relative to the phase ofthe respective second signal within the second signal set provided bythe signal source. Each respective second signal may include a number ofalternating HIGH periods and LOW periods within a predetermined timeduration, one pair of adjacent or consecutive HIGH and LOW periodsdefining a respective duty cycle. Each of the HIGH periods may have aduration substantially equal to a duration of a respective one of theLOW periods and may repeat with a frequency less than 2.5 Hertz. Each ofthe HIGH periods may be substantially equal to a respective one of theLOW periods and may repeat with a frequency equal to or less than 1Hertz. Each respective at least one signal within the second signal setprovided to each of the at least some of the plurality of transducerelements may include a number of alternating HIGH periods and LOWperiods within a predetermined time duration, one pair of adjacent HIGHand LOW periods defining a respective duty cycle. Each of at least oneof the HIGH periods and the LOW periods may include a plurality ofperiodic continuous signals. Each first signal set may vary based atleast on convective heat transfer changes proximate a respective one ofthe at least some of the plurality of transducer elements. Eachtransducer element of the at least some of the plurality of transducerelements may include at least one resistive member, each at least oneresistive member arranged to receive the respective at least one signalof the second signal set to vary temperature of the transducer elementof the at least some of the plurality of transducer elements. Eachsignal in each respective first signal set may include a number ofalternating HIGH periods and LOW periods within a predetermined timeduration, one pair of adjacent HIGH and LOW periods defining arespective duty cycle. The structure may be selectively configurablebetween a delivery configuration in which the structure ispercutaneously deliverable to the intra-cardiac cavity and an expandedconfiguration in which the structure is expanded within theintra-cardiac cavity, the structure sized too large to be deliveredpercutaneously to the intra-cardiac cavity in the expandedconfiguration. At least a first transducer element of the at least someof the plurality of transducer elements may be spaced on the structurefrom a second transducer element of the at least some of the pluralityof transducer elements such that at least the first transducer elementof the at least some of the plurality of transducer elements ispositioned on a portion of the structure lying across a portion of oneof the one or more ports and the second transducer element of the atleast some of the plurality of transducer elements is positioned on aportion of the structure which does not overlie the one of the one ormore ports when the structure is in the expanded configuration.

The medical system may further include an ablation source coupled totransfer energy between the ablation source and at least one of thetransducer elements.

The medical system may further include a radio-frequency generatorcoupled to provide a varying current to at least one transducer elementof the plurality of transducer elements to provide energy to the tissuewall from the at least one transducer element. The controller mayprovide the information in the form of a map of the location. of atleast one of the one or more regions of the interior surface of thetissue wall and the location of the at least one of the one or moreports relative to the location of the at least one of the one or moreregions of the interior surface of the tissue wall. The controller mayprovide a visual representation of the phase of each respective derivedfirst signal.

A medical system may be summarized as including a structure, one or moretransducer elements carried by the structure, the structure and the oneor more transducer elements sized to be received within an intra-cardiaccavity, the intra-cardiac cavity defined at least in part by a tissuewall with an interior surface of the tissue wall interrupted by one ormore ports positioned in fluid communication with the intra-cardiaccavity. The medical system includes a signal source providing arespective input signal to each of the one or more transducer elements.The medical system includes a sensing system sensing temperature changeat least proximate to each of the one or more transducer elements, thesensing system providing a respective set of one or more responsesignals for each of the one or more transducer elements, each set of oneor more response signals responsive to the temperature change at leastproximate to a respective one of the one or more transducer elements.The medical system includes a controller that derives at least onesignal from each set of one or more response signals and determines arespective set of one or more values representative of a phasedifference between each derived at least one signal and the respectiveinput signal provided to the transducer element of the one or moretransducer elements associated with the set of one or more responsesignals. The controller determines information specifying a location ofeach of one or more regions of the interior surface of the tissue walland a location of each of at least one of the one or more ports on theinterior surface of the tissue wall with respect to the one or moreregions based at least on each determined respective set of one or morevalues.

The signal source may provide a same or corresponding input signal toeach of the one or more transducer elements. The signal source mayprovide a single input signal to each of the one or more transducerelements. The one or more transducer elements may include a plurality oftransducer elements, and each respective input signal provided by thesignal source to each transducer element of the plurality of transducerelements may have a predetermined phase relative to the respective inputsignal provided to another transducer element of the plurality oftransducer elements. The one or more transducer elements may include aplurality of transducer elements, and each respective input signalprovided by the signal source to each transducer element of theplurality of transducer elements may have a different frequency than afrequency of the respective input signal provided to another transducerelement of the plurality of transducer elements.

The medical system may further include a synchronous demodulatorcommunicatively coupled between the controller and at least one of thetransducer elements to provide the phase of each derived at least onesignal relative to a phase of a respective signal provided by the signalsource. The controller may perform a frequency domain transform todetermine each respective set of one or more values. The controller mayperform a Fourier transform to determine each respective set of one ormore values. Each respective input signal may include a number ofalternating HIGH periods and LOW periods within a predetermined timeduration, one pair of adjacent HIGH and LOW periods defining arespective duty cycle. Each of at least one of the HIGH periods and theLOW periods of each respective input signal may include a plurality ofperiodic continuous signals. Each set of one or more response signalsmay include a voltage signal and an electrical current signal.

The medical system may further include an analog-to-digital converterarranged to sample each of the voltage signal and the electrical currentsignal in each set of one or more response signals synchronously withthe alternating HIGH periods and LOW periods of the respective inputsignal corresponding to the set of one or more response signals. Eachset of one or more response signals may include a voltage signal and anelectrical current signal. The sensing system may include one or moreresistance temperature detectors, the temperature change at leastproximate to each of the one or more transducer elements sensed by arespective one of the one or more resistance temperature detectors. Thestructure may be selectively configurable between a deliveryconfiguration in which the structure is percutaneously deliverable tothe intra-cardiac cavity and an expanded configuration in which thestructure is expanded within the intra-cardiac cavity, the structuresized too large to be delivered percutaneously to the intra-cardiaccavity in the expanded configuration. The one or more transducerelements may include a plurality of transducer elements, at least afirst transducer element of the plurality of transducer elements spacedon the structure from a second transducer element of the plurality oftransducer elements such that at least the first transducer element ofthe plurality of transducer elements is positioned on a portion of thestructure lying across a portion of one of the one or more ports and thesecond transducer element of the plurality of transducer elements ispositioned on a portion of the structure which does not overlie the oneof the one or more ports.

The medical system may further include an ablation source coupled totransfer energy to one or more transducer elements.

The medical system may further include a radio-frequency generatorarranged to provide a varying current to at least one transducer elementof the plurality of transducer elements to provide energy to the tissuewall from the at least one transducer element of the plurality oftransducer elements. The controller may provide the information in theform of a map of the location of at least one of the one or more regionsof the interior surface of the tissue wall and the location of the atleast one of the one or more ports relative to the location of the atleast one of the one or more regions of the interior surface of thetissue wall. The controller may provide a map of each determinedrespective set of one or more values.

A medical system may be summarized as including a structure and aplurality of transducer elements carried by the structure, the structureand the plurality of transducer elements sized to be received within anintra-cardiac cavity of a heart, the intra-cardiac cavity defined atleast in part by a tissue wall. An interior surface of the tissue wallis interrupted by one or more ports positioned in fluid communicationwith the intra-cardiac cavity. Each of at least some of the plurality oftransducer elements is responsive to blood flow proximate at leastproximate thereto. The medical system includes a controllercommunicatively coupled to the transducer elements and which determinesinformation that specifies a location of each of one or more regions ofthe interior surface of the tissue wall and a location of each of atleast one of the one or more ports on the interior surface of the tissuewall with respect to the one or more regions based at least in part on aphase of a blood flow signal indicative of the blood flow at leastproximate at least one of the transducer elements relative to a phase ofa drive signal supplied to the respective one of the transducerelements.

Various medical systems may include combinations and subsets of thosesummarized above.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, identical reference numbers identify similar elementsor acts. The sizes and relative positions of elements in the drawingsare not necessarily drawn to scale. For example, the shapes of variouselements and angles are not drawn to scale, and some of these elementsare arbitrarily enlarged and positioned to improve drawing legibility.Further, the particular shapes of the elements as drawn are not intendedto convey any information regarding the actual shape of the particularelements, and have been solely selected for ease of recognition in thedrawings.

FIG. 1 is a cutaway diagram of a heart showing a medical deviceaccording to one illustrated embodiment percutaneously placed in a leftatrium of the heart.

FIG. 2 is a partial schematic diagram of a medical system according toone illustrated embodiment, including a control system, a display, and amedical device having an expandable frame and an assembly of elements.

FIG. 3 is a cutaway diagram of a portion of an atrium and a number ofelements showing how the elements can sense convective cooling to locatea position of ports.

FIG. 4A is a top plan view of element construction for flow sensing.

FIG. 4B is a top plan view according to yet another illustratedembodiment

FIG. 4C is a top plan view according to yet another illustratedembodiment.

FIG. 4D is a top plan view according to yet another illustratedembodiment.

FIG. 4E is a top plan view according to yet another illustratedembodiment.

FIG. 4F is a top plan view according to yet another illustratedembodiment.

FIG. 4G is a top plan view according to yet another illustratedembodiment.

FIG. 4H is a top view according to yet another illustrated embodiment.

FIG. 5 is a diagram showing how common leads can be shared by elementsused for flow sensing according to various example embodiments.

FIG. 6 is a schematic view of a flexible circuit structure employed toprovide a plurality of transducer elements according to an exampleembodiment.

FIG. 7 is a circuit diagram of a system used for flow sensing, portlocation, and tissue ablation according to various example embodiments.

FIG. 8A is a block diagram of an electrical circuit that can be used todetermine a resistance of various resistive members employed by varioustransducer elements in various example embodiments.

FIG. 8B is an enlarged view of a source module of the block diagram ofFIG. 8A.

FIG. 8C is an enlarged view of a sensing system module of the blockdiagram of FIG. 8A.

FIG. 8D is an enlarged view of a controller module of the block diagramof FIG. 8A.

FIG. 9A is a series of graphs or plots of change in resistance versustime of a resistive member in each of “Flow” and “No Flow” conditions atrespective frequencies responsive to a first input condition accordingto various example embodiments.

FIG. 9B is a series of graphs or plots of change in resistance versustime of the resistive member in each of “Flow” and “No Flow” conditionsat respective frequencies responsive to a second input conditionaccording to various example embodiments.

FIG. 9C is a series of graphs or plots of change in resistance versustime of the resistive member in each of “Flow” and “No Flow” conditionsat respective frequencies responsive to a third input conditionaccording to various example embodiments.

FIG. 10A is a graph or plot of a Fourier power series magnitude versustime for a first resistive member under “Flow” and “No Flow” conditionsfor an 8-volt input voltage signal.

FIG. 10B is a graph or plot of a Fourier power series magnitude versustime for the first resistive member under “Flow” and “No Flow”conditions for a 4-volt input voltage signal.

FIG. 10C is a graph or plot of a Fourier power series magnitude versustime for the first resistive member under “Flow” and “No Flow”conditions for a 2-volt input voltage signal.

FIG. 10D is a graph or plot of a Fourier power series phase versus timefor the first resistive member under “Flow” and “No Flow” conditions foran 8-volt input voltage signal.

FIG. 10E is a graph or plot of a Fourier power series phase versus timefor the first resistive member under “Flow” and “No Flow” conditions fora 4-volt input voltage signal.

FIG. 10F is a graph or plot of a Fourier power series phase versus timefor the first resistive member under “Flow” and “No Flow” conditions fora 2-volt input voltage signal.

FIG. 11A is a graph or plot of a Fourier power series magnitude versustime for a second resistive member under “Flow” and “No Flow” conditionsfor an 8-volt input voltage signal.

FIG. 11B is a graph or plot of a Fourier power series magnitude versustime for the second resistive member under “Flow” and “No Flow”conditions for a 4-volt input voltage signal.

FIG. 11C is a graph or plot of a Fourier power series magnitude versustime for the second resistive member under “Flow” and “No Flow”conditions for a 2-volt input voltage signal.

FIG. 11D is a graph or plot of a Fourier power series phase for thesecond resistive member under “Flow” and “No Flow” conditions for an8-volt input voltage signal.

FIG. 11E is a graph or plot of a Fourier power series phase for thesecond resistive member under “Flow” and “No Flow” conditions for a4-volt input voltage signal.

FIG. 11F is a graph or plot of a Fourier power series phase for thesecond resistive member under “Flow” and “No Flow” conditions for a2-volt input voltage signal.

FIG. 12 is a graph or plot for a power series average phase value(radians) for each of a plurality of resistive members including thefirst resistive member of FIGS. 10A and 10B and the second resistivemember of FIGS. 11A and 11B in both the Flow and No Flow conditions.

DETAILED DESCRIPTION

In the following description, certain specific details are set forth inorder to provide a thorough understanding of various embodiments of theinvention. However, one skilled in the art will understand that theinvention may be practiced without these details. In other instances,well-known structures associated with radio-frequency (RF) ablation andelectronic controls such as multiplexers have not been shown ordescribed in detail to avoid unnecessarily obscuring descriptions of theembodiments of the invention. The word “ablation” should be understoodto mean any disruption to certain properties of the tissue. Mostcommonly, the disruption is to the electrical conductivity and isachieved by heating, which can be generated with resistive or ofradio-frequency (RF) techniques for example. Other properties, such asmechanical, or chemical and other means of disruption, such as optical,are included when the term “ablation” is used.

The word “fluid” should be understood to mean any fluid that can becontained within a bodily cavity or can flow into and/or out of a bodilycavity via one or more bodily openings positioned in fluid communicationwith the bodily cavity. In the case of cardiac applications, fluid suchas blood flows into and out of various intra-cardiac cavities (e.g., theleft atrium and the right atrium).

The word “bodily opening” should be understood to be a naturallyoccurring bodily opening or channel; a bodily opening or channel formedby an instrument or tool using techniques that can include, but are notlimited to, mechanical, thermal, electrical, chemical, and exposure orillumination techniques; a bodily opening or channel formed by trauma toa body; or various combinations of one or more of the above. A bodilyopening can include additional elements having respective openings orchannels and positioned within the bodily opening (e.g., a cathetersheath).

The word “tissue” should be understood to mean any tissue that is usedto form a surface within a bodily cavity, a surface of feature within abodily cavity, or a surface of a feature associated with a bodilyopening positioned in fluid communication with the bodily cavity. Thetissue can include part or all of a tissue wall or membrane thatincludes a surface that defines a surface of the bodily cavity. In thisregard, the tissue can form an interior surface of the cavity thatsurrounds a fluid within the cavity. In the case of cardiacapplications, tissue can include tissue used to form an interior surfaceof an intra-cardiac cavity such as a left atrium or right atrium.

The term “transducer element” (or “element” in some embodiments) in thisdisclosure should be interpreted broadly as any component capable ofdistinguishing between fluid and tissue, sensing temperature, creatingheat, providing energy (e.g., radio-frequency (RF)) energy, ablatingtissue and measuring electrical activity of a tissue surface, or anycombination thereof. A transducer element can convert input energy ofone form into output energy of another form. Without limitation, atransducer element can include an electrode operable to apply anelectrical signal to tissue or an electrode operable to generate anelectrical signal in response to a physical or electrical characteristicof tissue. Transducer elements may take the form of some othertransducer device, for example a transducer operable to apply energy to,or remove energy from, tissue. Alternatively, or additionally, atransducer element may take the form of some other transducer device,for example a transducer operable to sense a physical or othercharacteristic of tissue. A transducer element may be constructed fromseveral parts, which may be discrete components or may be integrallyformed.

Reference throughout this specification to “one embodiment” or “anembodiment” or “an example embodiment” means that a particular feature,structure or characteristic described in connection with the embodimentis included in at least one embodiment of the present invention. Thus,the appearances of the phrases “in one embodiment” or “in an embodiment”and the like in various places throughout this disclosure are notnecessarily all referring to the same embodiment. Furthermore, theparticular features, structures, or characteristics may be combined inany suitable manner in one or more embodiments.

Various embodiments of percutaneously or intravascularly deployedmedical devices are described herein. Many of the described devices aremoveable between an unexpanded configuration in which a portion of thedevice is sized for passage through a bodily opening leading to cavitywithin a body, and an expanded configuration in which the portion of thedevice expands within the bodily cavity. In some example embodiments,the device senses characteristics (e.g., convective cooling) thatdistinguish between fluid (e.g., blood) and tissue forming an interiorsurface of the bodily cavity. Such sensed characteristics allow amedical system to map the cavity, for example using positions ofopenings or ports into and out of the cavity to determine a position ororientation (i.e., pose), or both position and orientation of theportion of the device in the bodily cavity. In some example embodiments,the devices are capable of ablating tissue in a desired pattern withinthe bodily cavity. In some example embodiments, the devices are capableof sensing characteristics (e.g., electrical activity) indicative ofwhether an ablation has been successful.

An example of a mapping performed by devices according to variousembodiments is to locate the position of various bodily openings leadingto the pulmonary veins as well as the mitral valve on the interiorsurface of the left atrium. In some example embodiments, the mapping isbased at least on locating such bodily openings by differentiatingbetween fluid and tissue. There are many ways to differentiate tissuefrom a fluid such as blood or to differentiate tissue from a bodilyopening. One approach to determining the locations is to use theconvective cooling of heated transducer elements by the blood. Forexample, a slightly heated mesh of transducer elements that ispositioned adjacent to the tissue that forms the interior surface(s) ofthe atrium and across the ports of the atrium will be cooler at theareas which are spanning the ports carrying blood flow.

FIG. 1 shows a device 100 of a medical system useful in diagnosing ortreating a bodily organ, for example a heart 102, according to oneillustrated embodiment.

Device 100 can be percutaneously or intravascularly inserted into aportion of the heart 102, such as an intra-cardiac cavity like leftatrium 104. In this example, the device 100 is delivered via a catheter106 inserted via inferior vena cava 108 and penetrating through a bodilyopening in transatrial septum 110 from right atrium 112. In otherembodiments, other paths may be taken.

Catheter 106 is an elongated flexible rod member appropriately sized tobe delivered percutaneously or intravascularly. Catheter 106 may includeone or more lumens (not shown). The lumen(s) may carry one or morecommunications and/or power paths, for example one or more electricalconductors 116. Electrical conductors 116 provide electrical connectionsto device 100 that are accessible externally from a patient in whichdevice 100 is inserted.

As discussed in more detail herein, device 100 includes a structure orframe 118 which assumes a delivery or unexpanded configuration fordelivery to left atrium 104. Frame 118 is expanded (i.e., shown in adeployed or expanded configuration in FIG. 1) upon delivery to leftatrium 104 to position a plurality of transducer elements 120 (onlythree called out in FIG. 1) proximate the interior surface formed bytissue 122 of left atrium 104. In this example embodiment, at least someof the transducer elements 120 are used to sense a physicalcharacteristic of a fluid blood) or tissue 122, or both fluid and tissue122 that may be used to determine a position, orientation (i.e., pose),or both position and orientation of a portion of device 100 in leftatrium 104. For example, transducer elements 120 may be used todetermine a location of pulmonary vein ostiums (not shown), a mitralvalve 126, or both. In this example embodiment, at least some of thetransducer elements 120 may be used to selectively ablate portions ofthe tissue 122. For example, some of the elements may be used to ablatea pattern around the bodily openings, ports or pulmonary vein ostiums,for instance to reduce or eliminate the occurrence of atrialfibrillation.

FIG. 2 schematically shows a device 200 according to one illustratedembodiment. Device 200 includes a plurality of flexible strips 204(three called out in FIG. 2) and a plurality of transducer elements 206(three called out in FIG. 2) arranged to form a two- orthree-dimensional grid or array capable of mapping an inside surface ofa bodily cavity or lumen without requiring mechanical scanning. Theflexible strips 204 are arranged in a framed structure 208 that isselectively movable between an unexpanded configuration and an expandedconfiguration that may be used to force flexible strips 204 against atissue surface within the bodily cavity or position the flexible stripsin the vicinity of the tissue surface. The flexible strips 204 can formpart of a flexible circuit (also known as a flexible printed circuitboard (PCB) circuit). The flexible strips 204 can include a plurality ofdifferent material layers. The expandable frame 208 can include one ormore resilient members. Expandable frame 208 can include one or moreelongate members. Each of the one or more elongate members can include aplurality of different material layers. Expandable frame 208 can includea shape-memory material, for instance Nitinol Expandable frame 208 caninclude a metallic or non-metallic material by way of non-limitingexample. The incorporation of a specific material into expandable frame208 may be motivated by various factors including the specificrequirements of each of the unexpanded configuration and expandedconfiguration, the required position, orientation (i.e., pose), or bothposition and orientation of expandable frame 208 in the bodily cavityand the requirements for successful ablation of a desired pattern.

Expandable frame 208, as well as flexible strips 204, can be deliveredand retrieved via a catheter member, for example a catheter sheathintroducer 210. Flexible strips 204 may include one or more materiallayers. Flexible strips 204 may be made of one or more thin layers ofKapton® (polyimide), for instance 0.1 mm thick. Transducer elements(e.g., electrodes and/or sensors) 206 may be built on the flexiblestrips 204 using conventional printed circuit board processes. Anoverlay of a thin electrical insulation layer (e.g., Kapton® about 10-20micron thick) may be used to provide electrical insulation, except inareas needing electrical contact to blood and tissue. In someembodiments, flexible strips 204 can form a portion of an elongatedcable 216 of control leads 218, for example by stacking multiple layers,and terminating at a connector 220. In some example embodiments,flexible strips 204 are formed from flexible substrates onto whichelectrically conductive elements (e.g., conductive lines or traces) areprovided. In some example embodiments flexible strips 204 form flexiblecircuit structures. In some example embodiments, a portion of device 200is typically disposable.

Device 200 can communicate with, receive power from or be controlled bya control system 222 of the medical system. The control system 222 caninclude a controller 224 having one or more processors 226 and one ormore non-transitory storage media 228 that store instructions that areexecutable by the processors 226 to (a) process information receivedfrom device 200, (b) control operation of device 200 (e.g., activatingselected transducer elements 206 to ablate tissue, or both (a) and (b).Controller 224 can include one or more controllers. Control system 222may include an ablation source 230. The ablation source 230 may, forexample, provide electrical current or power, light or low temperaturefluid to the selected transducer elements 206 to cause ablation. Theablation source can include an electrical current source or anelectrical power source. Control system 222 can also include one or moreuser interface or input/output (I/O) devices, for example one or moredisplays 232, speakers 234, keyboards, mice, joysticks, track pads,touch screens or other transducers to transfer information to or from auser, for example a care provider such as a physician or technician. Forexample, output from the mapping process may be displayed on a display232.

While the embodiments disclosed above are described with examples ofcardiac mapping, the same or similar embodiments may be used for mappingother bodily organs, for example gastric mapping, bladder mapping,arterial mapping and mapping of any lumen or cavity into which thedevices of the present invention may be introduced. FIG. 3 shows aportion of a medical device 300, according to one illustratedembodiment.

The portion of the device 300 is particularly suitable to senseconvective cooling. Device 300 includes transducer elements 302 a, 302b, 302 c (collectively 302) capable of producing heat. Transducerelements 302 can, for example, be made of insulated resistive wire, suchas Nickel, or Nickel-Iron composition. The resistive wire may be mountedon an expandable frame 304. In this embodiment, the expandable frame 304can also be made of a material that has high impedance. Current passedthrough each transducer element 302 raises the temperature of thetransducer element 302 by a nominal amount. A rise of 0.5-3.0 degreesCelsius above normal blood temperature has been found to be sufficientin most cases. The power required to raise the temperature in thisparticular embodiment is about 10-50 mW per transducer element 302. Inthis illustrated embodiment which reflects a cardiac application, acentral one of the transducer elements 302 b, which is placed acrossport 306 of an ostium of pulmonary vein 308 will be cooled by blood flowmore than the neighboring transducer elements 302 a, 302 c which areadjacent to the inner or interior surface provided by tissue 310 thatsurrounds an intra-cardiac cavity (e.g., atrium 312). Transducerelements 302 which are found to be cooler on expandable frame 304indicate the locations of ports 306 in the tissue 310 that provides theatrium interior surface. This example embodiment need not requireintimate contact with tissue 310, since even at a distance of a fewmillimeters from the ports 306 the cooling effect is significantcompared to the cooling effect at a similar distance from the tissue 310of the heart wall. A backside (i.e., the side facing away from ports 306or tissue 310) of the transducer elements 302 may be thermally insulatedfor improved performance of both sensing and ablation. In this regard,the use of flat elongated members in the expandable frame 304 may beadvantageous. A cross-section of such a flat elongated member may, forexample have dimensions of 0.2 mm×2 mm for stainless steel or 0.3 mm×2.5mm for Nitinol. The insulation on the back side of the transducerelements 302 may take the form of a coat of silicone rubber. It isunderstood that other suitable materials or other suitable dimensionscan be employed in other example embodiments. In some embodiments, theelongate members may have varying cross-sectional dimensions as therespective lengths of the elongate members are traversed.

If the transducer elements 302 are made of a material that undergoes asignificant change in resistance with temperature, the temperature dropcan be determined from the resistance of the transducer element 302. Theresistance can be determined by measuring the voltage across thetransducer element 302 for a given current, or alternatively, bymeasuring the current through the transducer element 302 for a givenvoltage, for example via a Wheatstone bridge circuit. Some exampleembodiments may take advantage of convective cooling by the flow ofblood, and at least some of the transducer elements 302 function as ahot wire anemometer. Nickel wire is an example of a suitable material touse, as nickel is inert, highly resistive and has a significanttemperature coefficient of resistance (about 0.6% per deg. Celsius).Since the resistance of the transducer elements 302 can be made to berelatively low (i.e., typically less than 5 ohm), electrical noise canbe reduced and temperature changes as low as 0.1-1 deg. Celsius can bedetected. Several techniques can be employed to improve thissensitivity. One technique involves sampling the voltage waveform insynchronization with the heart rate. Another technique involves removingthe average voltage via AC coupling and only amplifying the voltagechange or derivative. Yet another technique involves passing the signalthrough a digital band pass filter having a center frequency trackingthe cardiac cycle, the pulmonary cycle, or both the cardiac and thepulmonary cycles.

FIGS. 4A-4H show various transducer element configurations according tovarious embodiments. Each of the embodiments of FIGS. 4A-4F showstransducer elements which have been constructed using microelectroniccircuit substrates, materials and techniques. Each of the embodiments ofFIGS. 4A-4F shows transducer elements which have been constructed intoflexible printed circuit boards (also known as flexible circuitstructures). Flexible circuit structures typically include a flexiblesubstrate layer that includes a dielectric material (e.g., polyester,LCP, polyimide) and an electrically conductive layer that includesvarious electrically conductive materials (e.g., gold or copper). Anelectrically conductive interconnection circuitry may be provided byvarious ones of the electrically conductive layers by various techniquesincluding sputtering, plating and etching, One or more material layers(e.g., adhesion layers, insulation layers) may be additionally providedin the flexible circuit structures.

The transducer elements may be affixed to a frame similar to theexpandable frame 208 shown in FIG. 2, which may be made from a materialsuch as Nitinol by way of non-limiting example. In some embodiments,each flexible circuit structure includes a plurality of substrates orplurality of material layers, at least one of the substrates or Materiallayers forming part of an expandable frame. In some example embodiments,the flexible substrates may be of such a thickness that the flexiblesubstrates can form the expandable frame. A flexible substrate made ofpolyimide having a thickness, for instance, of approximately 0.01-0.3 mmmay be suitable in some applications. In some applications, thetransducer elements can also be constructed using discrete components.The embodiments illustrated in FIGS. 4G-4H do not employ flexiblecircuits.

FIG. 4A shows a flexible circuit substrate 400 a that carries acombination of transducer elements, in particular sensor transducerelements 402 a, 402 b (collectively 402, only two called out in FIG. 4A)which sense convective cooling and ablation transducer elements 404 a,404 b (collectively 404, only two called out in FIG. 4A) which areoperable to ablate tissue. Leads, collectively 406, include electricallyconductive lines or traces that extend to respective ones of thetransducer elements 402, 404. The leads 406 may be coupled to a controlsystem (e.g., control system 222 of FIG. 2), which may provide (a)communications, (b) power, (c) control, or combinations of (a), (b) and(c) with the transducer elements 402, 404.

FIG. 4B shows a flexible circuit substrate 400 b that carries a numberof combined sensor and ablation transducer elements 408 a, 408 b(collectively 408, only two called out in FIG. 4B) that both sense flowand ablate non-blood tissue. This example embodiment may be asignificant advantage since a device with combined sensor and ablationtransducer elements 408 can measure flow at the exact spot that ablationwill occur, while requiring fewer components, thus improving precisionand reducing size. In this embodiment, each combined sensor and ablationtransducer element 408 has respective leads, collectively 410, coupledto a control system (e.g., control system 222 of FIG. 2).

A combined sensor and ablation transducer element 408 that can be usedfor both sensing flow and ablating can be made using standard printedcircuit construction processes. For example, a 2-4 mil copper trace on apolyimide substrate can be used. Copper changes resistance sufficientlyenough with temperature to be used to determine blood flow in a mannersimilar to that discussed above. Copper can also be used as an ablationelement by applying sufficient current through the copper to cause thecombined sensor and ablation transducer element 408 to heat resistively,for example to a temperature above 60° C. Power in the range ofapproximately 130-250 mW delivered to a copper pattern that has externaldimensions of 3 mm×1.0 mm and is thermally insulated on the side awayfrom the tissue may be sufficient to transmurally ablate a 3 mm deepsection of the tissue that surrounds at least a portion of the cavity.In this approach, the tissue is heated by conduction from the coppercombined sensor and ablation transducer element 408. When the tissue isheated by conduction, the combined sensor and ablation transducerelement 408 may be electrically insulated from the tissue.

Alternatively, the combined sensor and ablation transducer element 408can also be used to ablate tissue by using the combined sensor andablation transducer element 408 as an electrode for delivering RF energyto the tissue. In this scenario, electrical current is transferreddirectly to the tissue and the tissue is resistively heated by thecurrent flow. When RF energy is delivered, a preferred method may be tohave low electrical impedance between the combined sensor and ablationtransducer element 408 and the tissue. In some embodiments, anelectrically conductive electrode pad (not shown) is positioned betweensensor portions of transducer element 408 and the tissue. Delivering RFenergy is also possible if the combined sensor and ablation transducerelement 408 is capacitively coupled to the tissue, so long as theimpedance at the frequency of the employed RF energy is sufficiently low(i.e., typically under a few 100 ohms or less for a combined sensor andablation transducer element 408 of the size mentioned above). It isnoted that in the case where the combined sensor and ablation transducerelement 408 has a low electrical impedance connection to the tissue forlow frequencies, it is also possible to use the combined sensor andablation transducer element 408 to sense an electrical potential in thetissue that surrounds at least a portion of the heart cavity, forexample to generate an intra-cardiac electrogram. Thus, it is possiblefor the same combined sensor and ablation transducer element 408 tosense flow, sense electrical potential of the tissue that surrounds aportion of the heart cavity, and ablate the tissue. In some exampleembodiments, combined sensor and ablation transducer element 408 canalso stimulate (i.e., pace) tissue.

FIG. 4C shows a flexible circuit substrate 400 c that carries a numberof combined flow sensor, ablation and temperature transducer elements412 a, 412 b (collectively 412, only two called out in FIG. 4C) that canbe used to sense flow, ablate tissue that surrounds at least a portionof the heart cavity and sense or monitor temperature. The sensed ormonitored temperature can be used for ablation control, by way ofnon-example. A single control lead (three shown), collectively 414, isrequired per each combined flow sensor, ablation and temperaturetransducer element 412. A common return lead 416 is connected to themultiple combined flow sensor, ablation and temperature transducerelements 412. The combined flow sensor, ablation and temperaturetransducer element 412 can take the form of a low resistance resistor,for example a resistor formed by a 30-100 micron wide trace of 10-30micron thick copper foil. Such a resistor has a typical resistance of0.5-20 ohms and can be used as a combined flaw sensor, ablation andtemperature transducer element 412 to sense flow, perform ablation andsense temperature. When used as a temperature sensor, resistance changesof about 1% for a 2.5 degree Celsius temperature change are typical.

FIG. 4D shows a flexible circuit substrate 400 d that carries a numberof adjacent transducer elements 420 a, 420 b (collectively 420, only twocalled out in FIG. 4D). The transducer elements 420 share common controlleads 422. This feature is an advantage as it dramatically reduces thenumber of leads 422 needed to return to the control system (e.g.,control system 222 of FIG. 2).

FIG. 5 schematically shows an expanded example of a portion of theembodiment of FIG. 4D positioned proximate tissue 500. To determine flowby measuring the resistance of transducer element 420 b, the voltage atlead 422 a and lead 422 b should be made equal and the voltage at lead422 c and lead 422 d should be made equal, but to a different voltagethan that of lead 422 a and lead 422 b. In this condition, negligiblecurrent will flow through transducer element 420 a and transducerelement 420 c. Therefore, the current flowing through lead 422 b andlead 422 c is the same as the current flowing through the transducerelement 420 b, and the resistance of the transducer element 420 b can becalculated in a straightforward manner using the relationship V=I/R,where V is the voltage, I is the current and R is the resistance.

To cause the transducer element 420 b to heat to a temperaturesufficient to cause ablation, while not causing ablation at transducerelement 420 a and transducer element 420 c:

the voltage at lead 422 c and lead 422 d should be made equal;

the voltage at lead 422 b should be made higher than the voltage at lead422 c such that sufficient power is delivered to the transducer element420 b to cause the transducer element 420 b to heat to the appropriatetemperature; and

the voltage at lead 422 a should be set a value that is a fraction ofthat at lead 422 b such that the power delivered to the transducerelement 420 a is not sufficient to cause the temperature of thetransducer element 420 a to rise enough for tissue ablation.

For example, if the voltages at lead 422 c and lead 422 d are set to 0volts, voltage at lead 422 b is set to n volts and voltage at lead 422 ais set to ⅔ n volts, the power delivered to the transducer element 420 awill be only 11% of that delivered to the transducer element 420 b. Thistechnique of having adjacent transducer elements 420 share commoncontrol leads 422 can, for example, be used in a elongatedone-dimensional array of connected transducer elements 420 or may beapplied to transducer elements 420 connected in two-dimensional or inthree-dimensional arrays.

FIG. 4E shows a flexible circuit substrate 400 e that carries a numberof transducer elements 424 a, 424 b (collectively 424, only two calledout in FIG. 4E). The transducer elements 424 are coupled to leads 426,similar to leads 422 of the embodiment of FIG. 4D, and to additionalleads 428, which have been added to measure the voltage at the ends ofthe transducer elements 424. This feature advantageously increases theaccuracy in determining the resistance, and thus temperature, of thetransducer elements 424. The leads 426 that provide the current to thetransducer elements 424 typically have a small voltage drop across themthat can affect the accuracy of the resistance calculation of thetransducer element 424. The additional leads 428 will have a verylimited amount of current flowing through them, and thus the voltagedrop through the leads 428, even for a distance of several meters willbe negligible, and the voltage drop across the transducer elements 424can be determined accurately.

FIG. 4F shows a flexible circuit substrate 400 f that includes a mainbranch 435 and a plurality of side branches 437 (only two called out),each of these branches carrying various transducer elements. In thisillustrated embodiment, the branched flexible PCB substrate 400 f isleaf shaped, although it is understood that other shapes can be employedin other example embodiments of the invention. For example, various onesof side branches 437 can be disposed on each side of main branch 435.Additionally, side branches 437 can have different sizes than thoseillustrated in FIG. 4F. An expandable frame e.g., expandable frame 208of FIG. 2) may be covered by several of the branched substrates 400 f,each of which will cover or be proximate a respective portion of thetissue that forms an interior surface of the cavity of a bodily organwhen in use. Each of the branched substrates caries a plurality oftransducer elements 430 a, 430 b (collectively 430, only two called outin FIG. 4F). In this example, the transducer elements 430 are coupledtogether as described above in the embodiment of FIG. 4D. Leads 432(only one set shown) electrically connect each transducer element 430 toa control system (e.g., control system 222 of FIG. 2). The leads 432 cancouple power, communications or control signals. The leads 432 can, forexample, provide for electrically conductive coupling, inductivecoupling, capacitive coupling, optic coupling, galvanic coupling,fluidic coupling or thermal coupling by way of non-limiting example.

There are other approaches for creating transducer elements that do notrely on flexible circuit structures. FIGS. 4G and 4H provide examples ofsome of these.

FIG. 4G shows transducer elements 440 a, 440 b (collectively 440, onlytwo called out in FIG. 4G) that are made from a bundle of carbon fibers.Leads 442 couple the transducer elements 440 to a control system.

FIG. 4H shows transducer elements 450 a, 450 b (collectively 450, onlytwo called out in FIG. 4H) that are made directly from a hollow tube ofa metal such as stainless steel or alternatively from wire. Leads 452couple the transducer elements 450 to a control system.

The structures of the embodiments of FIGS. 4G and 4H may be advantageousin some embodiments, since the structures are relatively simple toassemble, and can be used directly as the supporting structure itself.Leads 442, 452 are connected at intervals to the carbon fiber or metal.The material between the leads 442, 452 form the transducer elements440, 450. In order to function properly, these transducer elements 440,450 should have electrical properties the same as, or similar to, theelectrical properties indicated previously. These two embodimentsprovide an example of where the same transducer element 440, 450 cansense flow, sense or measure temperature, deliver the ablation energy,be an integral component of the supporting structure, or any combinationof these functions.

FIGS. 4A-4H show examples of various transducer element configurationsthat can be employed in various embodiments. From the previousdescriptions, it is important to note that a single transducer elementcan sense blood flow in order to distinguish between blood and tissue,sense an electrical potential of the tissue e.g., heart wall), ablatetissue, sense or measure temperature, or form an integral component ofthe supporting structure, or any combination of these functions. Theablation may be performed by causing the transducer element to heat, orby delivering energy, such as radio-frequency (RF) energy directly tothe tissue. Also, transducer elements can be constructed usingindividual leads, common ground leads, or shared leads. Each lead mayhave a separate lead that runs in parallel to it for the purpose ofaccurately determining voltage potential directly at the transducerelement. As well, the examples discussed methods of sensing temperaturethat relied on changes in resistance. However, it is certainly possibleto use other temperature sensing methods, such as thermistors orthermocouples in con function with the transducer elements that produceheat. For example, the sensing transducer element of the embodiment ofFIG. 4A could be a thermistor, resistance temperature detector (RTD),thermocouple or temperature sensitive diode by way of non-limitingexample. In some example embodiments, a transducer element (e.g., aresistance temperature detector) can be used to induce a temperaturechange as well as sensing the temperature change.

FIG. 7 schematically shows an embodiment of an electric circuit 700 thatcan be used to distinguish between blood and tissue within a bodilycavity by sensing blood flow.

In this example embodiment, transducer elements 702 a-702 d(collectively 702) may be resistive elements, for example formed fromcopper traces on a flexible printed circuit board substrate, orresistive wires mounted on a structure. Each transducer element 702 isconnected by electronic transducer selection switches 704 a-704 h(collectively 704) to a single pair of conductors 706 a, 706 b(collectively 706) that provide a path out of the body via a cable 708.The transducer selection switches 704 may, for example be FET or MOSFETtype transistors. The transducer selection switches 704 will typicallyneed to carry significant power during the ablation phase. The cable 708may extend through a lumen of a catheter (not shown) or may otherwiseform part of a catheter structure.

The transducer selection switches 704 are selected by signals applied bya demultiplexer (selector) 710. The demultiplexer 710 may be controlledby a small number of conductors 712 (or even a single conductor if datais relayed in serial form). Conductors 706, 712 extend out of the bodyvia the cable 708. The transducer selection switches 704 and thedemultiplexer 710 may be built into a catheter (e.g., catheter 106 ofFIG. 1) near a distal end or point of deployment. The transducerselection switches 704 and demultiplexer 710 may be located within ornear the expandable frame e.g., expandable frame 208 of FIG. 2 in orderto minimize the number or length of the conductors extending through thecatheter.

At the other or proximate end of the catheter are a mode selectionswitch 726 and multiplexer 714. The mode selection switch 726 isoperable to select between a flow sensing mode (position shown in thedrawing) and an ablation mode (second position of the mode selectionswitch 726). In flow sensing mode, a current is created by a voltagesource 716 and resistor 718 (forming an approximate current source) androuted into a transducer element 702 selected via transducer selectionswitches 704. The two transducer selection switches 704 that areconnected to a given one of the transducer elements 702 to be used tosense flow are set to be closed and the remainder of the transducerselection switches 704 are set to be open. The voltage drop across thetransducer element 702 is measured via an analog-to-digital converter(ADC) 720 and fed to a controller (i.e., control computer 722).

It may be advantageous to use alternating current or a combination ofalternating current and direct current for sensing and ablation, forexample, direct current for ablation and alternating current forsensing. Alternating current approaches may also prevent errors fromelectrochemical potentials which could be significant if differentmetals come in contact with blood.

Determination of the location of the bodily cavity ports can be achievedby turning on all of transducer elements 702 sequentially or in groupsand determining a temperature by measuring the resistance of eachtransducer element 702. A map of the temperature of the transducerelements 702 may be formed in controller 722 or the controller 722 mayotherwise determine a position or orientation (e.g., pose) or both theposition and orientation of the device in the cavity. The transducerelements 702 with lower temperatures can correspond to ports leading tothe veins or valves when the bodily cavity is an intra-cardiac cavitysuch as a left atrium.

When mode selection switch 726 is set to select ablation, an ablationpower source 724 is connected sequentially to the transducer elements702 that are selected b the controller 722 by addressing the multiplexer714, which in turn controls the transducer selection switches 704 viathe demultiplexer 710. The ablation power source 724 can be an RFgenerator, or it can be one of several other power sources, several ofwhich are described below, If ablation power source 724 is an RFgenerator, the configuration of FIG. 7 implies unipolar RF ablation, inwhich current is fed into the tissue and passes to a ground (i.e., alsoreferred to as an indifferent electrode) connected to the body. Thecurrent that passes through the tissue causes the tissue to heat.However, bipolar ablation can be used as well. During bipolar ablation,current passes from a first one of the transducer elements 702 throughthe tissue to second one of the transducer elements 702. In someembodiments, each of the first one of the transducer elements 702 andthe second one of the transducer elements 702 is provided on a differentflexible circuit strip during the bipolar ablation. In some embodiments,the first one of the transducer elements 702 is provided on a flexiblecircuit strip that is spatially separated from a flexible circuit stripthat the second one of the transducer elements 702 is provided on duringthe bipolar ablation. In some embodiments, the first one of thetransducer elements 702 is provided on a portion of a support frame thatis spatially separated from a portion of the support frame that thesecond one of the transducer elements 702 is provided on during thebipolar ablation. A first one of the transducer elements 702 may beprovided on a portion of a support frame that is spatially separated bya spatial region from a portion of the support frame that a second oneof the transducer elements 702 is provided on, the spatial region notincluding any physical portion of the support frame. Other sources ofablation can be used besides radio-frequency sources. Frequencies fromDC to microwaves can be used, as well as delivery of laser power viaoptical fibers or cryogenics via thin tubes. For laser ablation, thetransducer selection switches 704 may take the form of optical switches.For cryogenic ablation, the transducer selection switches 704 may takethe form of suitable valves or actuators (e.g., solenoids).Alternatively, the bottom terminal of the lower switch of mode selectionswitch 726 may be coupled directly to ground. In this configuration, theablation power source 724 can be configured to supply current withfrequencies from DC to microwave, which will cause the selectedtransducer elements 702 to heat directly and produce ablation viathermal conduction.

During ablation it may be desirable to monitor the temperature of thetissue that forms the interior surface of the bodily cavity. The idealtemperature range for the tissue during ablation is typically 50-100° C.in some embodiments. Since this example embodiment includes temperaturemonitoring as part of the blood flow sensing, the progress of ablationcan be monitored by temporarily switching mode selection switch 726 to atemperature sensing position several times during the ablation.

FIG. 6 is a schematic view of a flexible circuit structure 600 employedto provide a plurality of transducer elements 602 (two called out)according to an example embodiment. Flexible circuit structure 600 canbe formed by various techniques including flexible printed circuittechniques. In this example embodiment, flexible circuit structure 600includes various layers including flexible layers 603 a, 603 b and 603 c(i.e., collectively flexible layers 603). In this example embodiment,each of flexible layers 603 includes or consists of at least oneelectrical insulator material (e.g., polyimide). One or more of theflexible layers 603 can include a different material than another of theflexible layers 603. In this example embodiment, various ones ofelectrically conductive layers 604 a, 604 b and 604 c (collectivelyelectrically conductive layers 604) are interposed between orinterleaved with the flexible layers 603. In this example embodiment,each of the electrically conductive layers 604 is deposited or patternedto form various electrically conductive members. For example,electrically conductive layer 604 a is deposited or patterned to form arespective electrode 606 (two called out) of each of the transducerelements 602. Electrically conductive layer 604 b is deposited orpatterned to form respective temperature sensors 608 for each of thetransducer elements 602 as well as various traces or leads 610 aarranged to provide electrical energy to the temperature sensors 608. Inthis example embodiment, each temperature sensor 608 includes adeposited or patterned resistive member 609 (two called out) having apredetermined electrical resistance. In this example embodiment, eachresistive member 609 includes a metal having relatively high electricalconductivity characteristics (e.g. copper). In this example embodiment,electrically conductive layer 604 c is deposited or patterned to provideportions of various traces or leads 610 b arranged to provide anelectrical communication path to electrodes 606. In this exampleembodiment, traces or leads 610 b are arranged to pass though vias (notshown) in flexible layers 603 a and 603 b to couple with electrodes 606.

In various example embodiments, electrodes 606 are employed toselectively deliver RF energy to various tissue structures within anintra-cardiac cavity (not shown). In various example embodiments, eachelectrode 606 is employed to sense an electrical potential in the tissueproximate the electrode 606. In various example embodiments, eachelectrode 606 is employed in the generation of an intra-cardiacelectrogram. In this example embodiment, each resistive member 609 ispositioned directly adjacent a respective one of the electrodes 606.Each resistive member 609 is positioned in a stacked or layered arraywith a respective one of the electrodes 606 to form a respective one ofthe transducer elements 602. In this example embodiment, the resistivemembers 609 are connected in series to allow electrical current to passthrough all of the resistive members 609. In this example embodiment,traces or loads 610 a are arranged to allow for a sampling of electricalvoltage between associated resistive members 609. This arrangementallows for the electrical resistance of each resistive member 609 to beaccurately measured.

FIG. 8A is a block diagram of an electrical circuit 800 that can be usedto determine an electrical resistance of various resistive members(e.g., resistive members 609) employed by various transducer elements(e.g., transducer elements 602) in various example embodiments. In thisexample embodiment, a plurality of transducer elements 802 a, 802 b, . .. 802 n (collectively 802) can be positioned on a structure (e.g. frame208) that is configurable between an unexpanded or deliveryconfiguration in which the structure is suitably sized for percutaneousdelivery to a bodily cavity (e.g., left atrium 104) having one or moreports (e.g., pulmonary vein ostiums (not shown) or a mitral valve 126)in fluid communication with the bodily cavity and an expanded ordeployed configuration in which the transducer elements are repositionedwithin the bodily cavity. In some embodiments, the structure may be toolarge for percutaneous delivery to the bodily cavity in theexpanded/deployed configuration. At least a first transducer element 802can be spaced on the structure from a second transducer element 802 suchthat at least the first transducer element 802 is positioned on aportion of the structure lying across a portion of one of the one ormore ports and the second transducer element 802 of the plurality oftransducer elements 802 is positioned on a portion of the structurewhich does not overlie the one of the one or more ports when thestructure is in the expanded/deployed configuration. The number oftransducer elements 802 employed can vary in different embodiments.

In this example, each transducer element 802 includes a respectiveresistive member 809 (three called out in FIG. 8A), for example formedfrom copper traces on a flexible printed circuit board substrate, orresistive elements provided on a structure. Each transducer element 802is driven by a state machine (not shown within controller 822. In thisexample embodiment, electrical circuit 800 includes a signal source 812(i.e., an enlarged view shown in FIG. 8B), a sensing system 816 (i.e.,an enlarged view shown in FIG. 8C) and controller 822 (i.e., an enlargedview shown in FIG. 8D), each schematically distinguished from oneanother by broken lines for clarity. It is understood that each ofsignal source 812, sensing system 816 and controller 822 may eachinclude different circuitry than those shown in FIG. 8A and respectiveones of FIGS. 8B, 8C and 8D.

In this example embodiment, signal source 812 is used to provide varioussignals. In some embodiments, signal source 812 provides at least onesignal having a number of alternating “HIGH” and “LOW” periods within apredetermined time duration. One set of HIGH and LOW periods may definea duty cycle in some embodiments. Each of at least one of the HIGHperiods and the LOW periods may include a plurality of periodiccontinuous signals. It is understood that signal source 812 can providesignals having other waveforms in other embodiments.

In some embodiments, signal source 812 provides various input signals toat least some of the transducer elements 802 during a temperaturesensing mode. In some embodiments, signal source 812 provides variousinput signals to at least some of the transducer elements 802 during aflow sensing mode. In some example embodiments, signal source 812provides various input signals to ouch of the transducer elements 802during a mapping mode in which information specifying a location ofvarious anatomical features within a bodily cavity is provided. Forexample, information specifying a location of each of one or moreregions of an interior tissue surface within an intra-cardiac cavity maybe provided along with information specifying a location of each of atleast one of one or more ports on the interior tissue wall with respectto the one or more regions during the mapping mode. In some exampleembodiment, signal source 812 provides various input signals during anablation mode.

Signal source 812 can include one or more sources configured to providea set of one or more signals. In this example embodiment, a statemachine (not shown) in controller 822 may be employed to cause variouscontrol signals (not shown) to be provided to signal source 812 toconfigure electrical circuit 800 in at least one of a temperaturesensing mode and a flow sensing mode. In some example embodiments,signal source 812 includes an ablation source (e.g., ablation source724) coupled to transfer energy to, or from, the tissue wall via one ormore transducers. The coupling may for example be an electrical orthermal direct connection or indirect connection. In some exampleembodiments, signal source 812 includes a radio frequency generatorarranged to provide a varying electrical current to at least one of thetransducer elements 802 to provide energy to tissue from the at leastone of the transducer elements 802.

In this illustrated embodiment, digital-to-analog converter (DAC) 814generates an input signal that is amplified and is driven across theseries of the connected resistive members 809 during a temperaturesensing mode. Amplifiers including driver 815 a and driver 815 b arearranged to produce a balanced output across the series of connectedresistive members 809. Electrical current driven through resistivemembers 809 is sampled by sensing system 816. In this exampleembodiment, electrical current driven through resistive members 809 issampled at each of the drivers 815 a, 815 b via respective ones ofanalog-to-digital converters (ADC) 818 a, 818 b. It is noted thatsensing the electrical current at each of the drivers 815 a, 815 b canallow the system to detect possible failures that may result in theelectrical current leaking through another path. Voltage across each ofthe resistive members 809 is also sampled by sensing system 816 viarespective ones of analog-to-digital converters (ADC) 819 (three calledout in each of FIGS. 8A and 8C). In this example embodiment, the currentand voltage measurements are sampled synchronously with the input signaland the demodulation of each measurement is computed by controller 822.Electrical circuit 800 allows for the electrical resistance of each ofthe resistive members 809 to be precisely measured. The resistance of anelectrically conductive metal (e.g., copper) changes based on thetemperature of the electrically conductive metal. The rate of change isdenominated as a temperature coefficient of resistance (TCR). Theresistance of various ones of the resistive members 809 may be relatedto the temperature of the resistor element 809 by the followingrelationship:

R=R ₀*[1+TCR*(T−T ₀)],

where:

R is a resistance of the electrically conductive metal at a temperatureT;

R₀ is a resistance of the electrically conductive metal at a referencetemperature T₀;

TCR is the temperature coefficient of resistance for the referencetemperature i.e., the TCR for copper is 4270 ppm at T₀=0° C.); and

T is the temperature of the electrically conductive metal.

In this example embodiment, flow sensing is measured by electricalcircuit 800 by measuring the rate of convective cooling at various onesof the resistive members 809. In this example embodiment, when the flowsensing mode is enabled, various ones of the resistive members 809 whosetemperature is measured during the temperature sensing mode can also beemployed to deliver energy (i.e., heat) during the flow sensing mode. Inthis example embodiment, the energy is delivered using the same drivers815 a, 815 b employed in the temperature sensing mode. It is understoodthat additional and or alternate drivers may be employed in otherexample embodiments but with additional cost and complexity. When thetemperature sensing mode is not active, the state machine in controller822 continues to drive an input signal to each of the resistive members809 in this example embodiment.

In this example embodiment, a flow sense control signal 824 is employedto enable or disable flow sensing capability. In this exampleembodiment, flow sense control signal 824 is modulated using flow sensecarrier signal 826. In some embodiments, flow sense carrier signal 826can include a number of alternating “HIGH” and “LOW” periods within apredetermined time duration. Respective sets of adjacent HIGH and LOWperiods may define a duty cycle. Each of at least one of the HIGHperiods and the LOW periods may include a plurality of periodiccontinuous signals. In this example embodiment, flow sense controlsignal 824 is modulated using a 1-Hertz (Hz) square-wave flow sensecarrier signal 826. It is understood that the flow sense carrier signal826 can include other waveforms in other example embodiments. In thisexample embodiment, the resulting signal is summed with a temperaturesense control signal 828 which introduces a relatively small signal thatallows temperature to be sensed regardless of the state of the flowsense control signal 824. In this example embodiment, the combinedtemperature sense control signal 828 and modulated flow sense controlsignal 824 is further modulated using a 25 kHz square wave temperaturesense carrier signal 830. The additional modulation may be motivated forvarious reasons. For example, the additional modulation may be performedto ensure that the patient is not exposed to low frequency signals.Temperature sense carrier signal 830 may include other waveforms inother example embodiments.

In this example embodiment, a 25 kHz input signal (not shown) resultsand is provided by signal source 812 across each of the resistivemembers 809. In this example embodiment, electrical current passingthrough resistive members 809 is sampled at each of the drivers 815 a,815 b via respective ones of analog-to-digital converters (ADC) 818 aand 818 b. Voltage across each of the resistive members 809 is alsosampled via respective ones of analog-to-digital converters (ADC) 819.In various example embodiments, a respective first signal set of one ormore signals is provided by each transducer element 802 to controller822. In this example embodiment, each respective first signal setincludes a signal representative of a measured voltage across arespective one of the resistive members 809 as sensed by sensing system816. At least one signal representative of a measured electrical currentthrough each respective resistive member 809 is also provided by sensingsystem 816 to controller 822.

In this example embodiment, each of the signals representative of themeasured electrical currents and voltages associated with eachtransducer element 802 are demodulated synchronously with thetemperature sense carrier signal 830 by a respective synchronousdemodulator 834 (five called out in each of FIGS. 8A and 8D). It isnoted that although signals provided via respective ones ofanalog-to-digital converters (ADC) 818 a and 818 b are also demodulatedsynchronously with the temperature sense carrier signal 830 by arespective synchronous demodulator 834 in this illustrated embodiment,other different synchronous demodulators may be used in otherembodiments. In this example embodiment, each of a plurality ofcontroller modules 836 (five called out in each of FIGS. 8A and 8D)selects the in-phase component of a respective one of the variousdemodulated signals. In this example embodiment, various controllermodules 838 (three called out in each of FIGS. 8A and 8D) processesvarious sets of the in-phase components to determine electricalresistance information for each of the resistive members 809. In thisexample embodiment, controller modules 838 further process theelectrical resistance information to determine temperature informationfor each of the resistive members 809.

In this example embodiment, a synchronous demodulator 840 (three calledout in each of FIGS. 8A and 8D) is employed to synchronously demodulatea signal including or encoding temperature information associated with arespective one of the resistive members 809 with the flow sense carriersignal 826. In some example embodiments, a synchronous demodulator 840(three called out in each of FIGS. 8A and 8D) is employed tosynchronously demodulate a signal including electrical resistanceinformation associated with a respective one of the resistive members809 with the flow sense carrier signal 826. In this example embodiment,controller module 842 (three called out in each of FIGS. 8A and 8D) isused to determine phase information of the demodulated signal providedby a respective one of the synchronous demodulators 840. In this exampleembodiment, the phase information is provided by a respective flow senseresult signal 844 (three called out in each of FIGS. 8A and 8D) providedby the controller module 842.

In this example embodiment, each controller module 842 determinesinformation representing the phase of a first signal derived at least inpart from the first signal set provided by a respective one of thetransducer elements 802 relative to a phase of a second signal (e.g.,flow sense carrier signal 826 in this illustrated embodiment) of arespective second signal set provided by signal source 812. In variousexample embodiments, signal source 812 provides a respective inputsignal to each transducer element 802, and sensing system 816 provides arespective set of one more response signals (e.g., voltage and currentsignals in this example embodiment) responsive to at least a temperaturechange at least proximate to the respective transducer element 802. Inthese various embodiments, controller 822 derives at least one signalfrom each set of one or more response signals and determines arespective set of one or more values representative of a phasedifference between each derived at least one signal and the respectiveinput signal provided to the transducer element 802 associated with theset of one or more response signals. In some of the various embodiments(e.g., this example embodiment), signal source 812 provides a same inputsignal to each of the transducer elements 802. In some of the variousembodiments, each respective input signal provided by signal source 812to at least one of the transducer elements 802 has a predetermined phasedifference relative to the respective input signal provided to anotherof the transducer elements 802. In some of the various embodiments,signal source 812 provides a plurality of signals, at least one of thesignals having a predetermined phase difference relative to another ofthe plurality of signals. In some of the various embodiments, controller822 determines the respective set of one or more values representativeof a phase difference between each derived at least one signal and therespective input signal provided to the transducer element 802associated with the set of one or more response signals based on areference signal having a predetermined phase relative to the respectiveinput signal provided to the transducer element 802 associated with theset of one or more response signals.

In various example embodiments in which the plurality of transducerelements 802 are arranged within a bodily cavity (e.g., an intra-cardiaccavity such as a left atrium) having various internal anatomicalfeatures, controller 822 can provide information specifying a locationof at least one of the internal anatomical features within the bodilycavity based at least in part on the phase information of thedemodulated signal provided by a respective one of the synchronousdemodulators 840. As an example, the plurality of transducer elements802 may be arranged within a bodily cavity (e.g., an intra-cardiaccavity such as a left atrium 104) defined at least in part by a tissuewall having an interior tissue surface interrupted by one or more portsin fluid communication with the bodily cavity (e.g., pulmonary veins).In such an example, the controller 822 can provide informationspecifying a location of each of one or more regions of the interiortissue surface and a location of at least one of the one or more portson the interior tissue surface with respect to the one or more regions.The information may be determined by controller 822 based at least inpart on the phase of a first signal derived at least in part from afirst signal set provided by respective ones of the transducer elements802 relative to a phase of a second signal (i.e., flow sense carriersignal 826 in this illustrated embodiment) of a respective second signalset provided by signal source 812. In various example embodiments inwhich signal source 812 provides a respective input signal to eachtransducer element 802 and sensing system 816 provides a respective setof one more response signals (i.e., voltage and current signals in thisexample embodiment) responsive to at least a temperature change at leastproximate to the transducer demerit 802, controller 822 can provideinformation specifying a location of each of one or more regions of theinterior tissue surface and a location of at least one of the one ormore ports on the interior tissue surface with respect to the one ormore regions. The provided information may be based at least in part oninformation including a respective set of one or more valuesrepresentative of a phase difference between at least one signal derivedfrom each respective set of one or more response signals and therespective input signal provided to the respective transducer element802 associated with the set of one or more response signals. In someembodiments, controller 822 provides information specifying a locationof each of one or more regions of the interior tissue surface and alocation of at least one of the one or more ports on the interior tissuesurface with respect to the one or more regions in the form of a map. Insome example embodiments, controller 822 provides a visualrepresentation of the phase of each signal derived from various signalsprovided by sensing system 816 relative to the phase of a respectivesignal provided by the set of one or more signals outputted by signalsource 812. Various displays or other output devices or systems (e.g.,display 232) may be employed to provide information from controller 822to a user (e.g., a health care provider).

The present inventors have noted that when a signal source appliesenergy to a resistive element (e.g., resistive member 809 employed byvarious transducer elements 802) positioned within a medium havingrelatively high flow conditions, for example when subjected to bloodflow conditions proximate to a pulmonary vein port in the left atrium ofa heart, the resistive element will heat to a lower temperature and willsettle more quickly than if the resistive element were to be positionedwithin a medium having relatively low flow conditions, for example whenpositioned proximate to, or in contact with a region of a tissue surfacewithin a left atrium positioned away from the pulmonary vein port.Likewise, when the signal source ceases to apply energy, the resistiveelement positioned within a medium having relatively high flowconditions will cool faster and will return to ambient temperaturefaster than if the resistive element were to be within a medium havingrelatively lower flow conditions. When the signal source repetitivelyapplies and ceases to apply energy to the resistive element, theresulting temperature changes of the resistive element positioned in amedium having relatively low flow conditions will appear to have a phasedelay compared to the resulting temperature changes of the resistiveelement when positioned in a medium having relatively higher flowconditions.

EXAMPLES

The following are examples of various example embodiments. It isunderstood that other embodiments are not so limited, as alternativeembodiments have been provided and will become readily apparent to thoseof ordinary skill in the art.

A device having a framed structure made up of a plurality of elongatemembers arranged in an expanded configuration similar to thatillustrated in FIGS. 1 and 2 was employed in these examples. Eachelongate member was made up of a resilient metallic material (e.g.,stainless steel) sheathed in an electrical insulator material (i.e.,polyimide). Attached to each of a subset of four (4) of the elongatemembers, denominated herein as elongate members #1, #2, #3 and #4 (atleast some referred to in some of the graphs provided by FIGS. 10, 11and 12), was a respective flexible circuit structure i.e., similar tothat shown in FIG. 6). Each flexible circuit structure provided nine (9)transducer elements, each transducer element including a resistivemember (i.e., similar to resistive members 609), with power arranged tobe selectively provided to each resistive member. The device wasinserted into a water bath and a multi-hole nozzle was arranged toselectively establish flow conditions within the bath. The nozzle wascontrolled to selectively expose the resistive members to a relativelylow flow condition (i.e., essentially a stagnant bath) herein referredto as a “No Flow” condition and a relatively high flow condition hereinreferred to as a “Flow” condition. Various ones of resistive memberswere spatially arranged to experience different degrees of the flow inthe Flow condition. In this example embodiment, power provided to eachresistive member was modulated in each of the Flow and No Flowconditions. Each modulated cycle included a period where constantmodulated voltage was applied to each resistive member followed by aperiod where minimal voltage was provided to the resistive member (i.e.,voltage sufficient to measure the resistance with minimal heating). Eachresistive member was subject to voltages that were varied between three(3) levels (i.e., 2V, 4V and 8V), each level provided at each of asignal frequency that was varied between three (3) levels (i.e., 0.5 Hz,1 Hz and 5 Hz) in each of the Flow and No Flow conditions. An electricalresistance plot for each resistive member was produced for each of thesevarious power conditions.

FIGS. 9A, 9B and 9C show a series of graphs or plots of change inresistance (in milli-ohms) over a selected number of time periods (inseconds) of one of the resistive members in each of the Flow and No Flowconditions under the influence of various voltage signals. Specifically,FIG. 9A includes respective graphs or plots of change in resistanceversus time of a resistive member in response to an application ofelectrical power (e.g., voltage and/or current) at each of 2 V, 0.5 Hz;2 V, 1 Hz; and 2 V, 2.5 Hz conditions. FIG. 9B includes graphs or plotsof change in resistance versus time of the resistive member in responseto an application of power at each of 4 V, 0.5 Hz; 4 V, 1 Hz; and 4 V,2.5 Hz conditions. FIG. 9C includes graphs or plots of change inresistance versus time of the resistive member in response to anapplication of power at each of 8 V, 0.5 Hz; 8 V, 1 Hz; and 8 V, 2.5 Hzconditions. In this example embodiment, the Flow conditions arerepresented by the broken line traces while the No Flow conditions arerepresented by the continuous line traces. Upon initial inspection ofthe graphs or plots there appears to be little discrimination betweenthe traces representing the Flow conditions and their correspondingtraces representing the No Flow conditions. Some of the tracesrepresenting the Flow conditions for various ones of the 0.5 Hz and 1 Hzcases generally appear to have a somewhat squarer shape than theircorresponding traces representing the No Flow conditions. In thisexample embodiment, a frequency domain transform was employed to furtherdistinguish the traces. In this example embodiment, a Fourier powerseries was applied over an integral number of periods. The magnitude andphase response of the Flow and No Flow cases for each of the resistivemembers was compared. For each frequency, the number of periods waschosen as the least common multiple between all of the periods to alloweach power series to use the same number of samples. The results forvarious ones of the resistor elements are provided in the followingexamples.

Example 1

FIGS. 10A, 10B and 10C show graphs or plots of power series magnitude(in volts) versus time for a first one of the resistive members(denominated as elongate member #1, resistive member #4) in response toa variety of input voltage signals with the following pairs of signalcharacteristics: 8 V, 0.5 Hz; 8 V, 1 Hz; and 8V, 2.5 Hz as shown in FIG.10A; 4 V. 0.5 HZ; 4V, 1 HZ; and 4 V. 2.5 Hz as shown in FIG. 10B; and 2V, 0.5Hz; 2 V, 1 Hz; and 2 V, 2.5 Hz as shown in FIG. 10C. FIGS. 10D,10E and 10F respectively show graphs or plots of power series phase (inradians) versus time for the first one of the resistive members(denominated as elongate member #1, resistive member #4) in response toa variety of input voltage signals with the following pairs of signalcharacteristics: 8V, 0.5Hz; 8 V, 1 Hz; and 8V, 2.5 Hz as shown in FIG.10D; 4 V. 0.5 Hz; 4 V, 1 Hz; and 4 V, 2.5 Hz as shown in FIG. 10E; and2V, 0.5 Hz; 2 V, 1 Hz; and 2 V, 2.5 Hz as shown in FIG. 10F. The resultsfor the Flow conditions are represented by the symbol “o” in each graphor plot while the results for the No Flow conditions are represented bythe symbol “+” in each graph or plot. It is evident from the graphs orplots of FIGS. 10A, 10B and 10C that a lack of substantialdifferentiation exists between the magnitude values corresponding to theFlow conditions and the magnitude values corresponding to the No Flowconditions for this particular resistive member. However, the plots ofFIGS. 10D, 10E and 10F show that a noticeable differentiation existsbetween the phase values corresponding to the Flow conditions and thephase values corresponding to the No Flow conditions for this particularresistive member for the 1Hz voltage signals and an even more pronounceddifferentiation exists between the phase values corresponding to theFlow conditions and the phase values corresponding to the No Flowconditions for this particular resistive member for the 0.5 Hz voltagesignals.

Example 2

FIGS. 11A, 11B and 11C respectively show graphs or plots of power seriesmagnitude (in volts) versus time for a second one of the resistivemembers (denominated as elongate member #2, resistive member #3) inresponse to a variety of input voltage signals with the following pairsof signal characteristic: 8 V, 0.5 Hz; 8 V, 1 Hz; and 8 V, 2.5 Hz asshown in FIG. 11A; 4 V, 0.5 Hz; 4 V, 1 Hz; and 4 V, 2.5 Hz as shown inFIG. 11B; and 2 V, 0.5 Hz; 2 V, 1 Hz; and 2 V, 2.5 Hz as shown in FIG.11C. FIGS. 11D, 11E and 11F respectively show graphs or plots of powerseries phase (in radians) versus time for the second one of theresistive members (denominated as elongate member #2, resistive member#3) in response to a variety of the input voltage signals with thefollowing pairs of signal characteristic: 8 V, 0.5 Hz; 8 V, 1 Hz; and 8V, 2.5 Hz as shown in FIG. 11D; 4 V, 0.5 Hz; 4 V, 1 Hz, and 4 V, 2.5 Hzas shown in FIG. 11E; and 2 V, 0.5 Hz; 2 V, 1 Hz; and 2V, 2.5 Hz asshown in FIG. 11F. The results for the Flow conditions are representedby the symbol “o” in each plot while the results for the No Flowconditions are represented by the symbol “+” in each plot. In a similarmanner to that shown in FIGS. 10A, 10B and 10C, the graphs or plots inFIGS. 11A, 11B and 11C also show a lack of substantial differentiationbetween the magnitude values corresponding to the Flow conditions andthe magnitude values corresponding to the No Flow conditions for thisparticular resistive member. However, the graphs or plots of FIGS. 11D,11E and 11F show that a noticeable differentiation exists between thephase values corresponding to the Flow conditions and the phase valuescorresponding to the No Flow conditions for this particular resistivemember for the 1 Hz voltage signals and an even more pronounceddifferentiation exists between the phase values corresponding to theFlow conditions and the phase values corresponding to the No Flowconditions for this particular resistive member for the 0.5 Hz voltagesignals.

Similar results were also obtained for other ones of the resistivemembers. FIG. 12 shows a graph or plot for power series average phasevalue (in radians) versus time for each of the tested resistive membersin both the Flow and No Flow conditions under the influence of or inresponse to an input voltage signal with 8 V, 0.5 Hz signalcharacteristics. The results for the Flow conditions are represented bythe symbol “o” in each plot while the results for the No Flow conditionsare represented by the symbol “+” in each plot. In this graph or plot,the resistive members denominated as #1 through #9 of elongate member #1are identified by respective numbers 1 through 9 on the x axis. Theresistive members denominated as #1 through #9 of elongate member #2 areidentified by respective numbers 10 through 18 on the x axis. Theresistive members denominated as #1 through #9 of elongate member #3 areidentified by respective numbers 19 through 27 on the x axis. Theresistive members denominated as #1 through #9 of elongate member #4 areidentified by respective numbers 28 through 36 on the x axis. The graphor plot of FIG. 12 shows that a noticeable differentiation existsbetween the phase values corresponding to the Flow conditions and thephase values corresponding to the No Flow conditions for each of theelements under these input conditions. It is noted that larger phasedifferences between the Flow and No Flow conditions exist for the“higher” numbered resistive members positioned on each of the fourelongate members indicating that these particular resistive members werepositioned to experience greater flow conditions.

While the embodiments disclosed above are described with examples ofcardiac mapping, the same or similar embodiments may be used for mappingother bodily organs, for example gastric mapping, bladder mapping,arterial mapping and mapping of any lumen or cavity into which thedevices of the present invention may be introduced.

While the embodiments disclosed above are described with examples ofcardiac ablation, the same or similar embodiments may be used forablating other bodily organs or any lumen or cavity into which thedevices of the present invention may be introduced.

The various embodiments described above can be combined to providefurther embodiments. All of the U.S. patents, U.S. patent applicationpublications, U.S. patent applications, foreign patents, foreign patentapplications and non-patent publications referred to in thisspecification and/or listed in the Application Data Sheet areincorporated herein by reference, in their entirety. Aspects of theinvention can be modified, if necessary, to employ systems, circuits andconcepts of the various patents, applications and publications toprovide yet further embodiments of the invention.

These and other changes can be made to the invention in light of theabove-detailed description. In general, in the following claims, theterms used should not be construed to limit the invention to thespecific embodiments disclosed in the specification and the claims, butshould be construed to include all medical treatment devices inaccordance with the claims. Accordingly, the invention is not limited bythe disclosure, but instead its scope is to be determined entirely bythe following claims.

1. A medical system, comprising: a structure; one or more transducerelements carried by the structure, the structure and the one or moretransducer elements sized to be received within an intra-cardiac cavity,the intra-cardiac cavity defined at least in part by a tissue wall,wherein an interior surface of the tissue wall is interrupted by one ormore ports positioned in fluid communication with the intra-cardiaccavity; a signal source providing a respective input signal to each ofthe one or more transducer elements; a sensing system sensingtemperature change at least proximate to each of the one or moretransducer elements, the sensing system providing a respective set ofone or more response signals for each of the one or more transducerelements, each set of one or more response signals responsive to thetemperature change at least proximate to a respective one of the one ormore transducer elements; and a controller that derives at least onesignal from each set of one or more response signals and determines arespective set of one or more values representative of a phasedifference between each derived at least one signal and the respectiveinput signal provided to the transducer element of the one or moretransducer elements associated with the set of one or more responsesignals, and which determines information specifying a location of eachof one or more regions of the interior surface of the tissue wall and alocation of each of at least one of the one or more ports on theinterior surface of the tissue wall with respect to the one or moreregions based at least on each determined respective set of one or morevalues.
 2. The medical system of claim 1 wherein the signal sourceprovides a same input signal to each of the one or more transducerelements.
 3. The medical system of claim 1 wherein the one or moretransducer elements comprise a plurality of transducer elements, andeach respective input signal provided by the signal source to eachtransducer element of the plurality of transducer elements has apredetermined phase relative to the respective input signal provided toanother transducer element of the plurality of transducer elements. 4.The medical system of claim 1, further comprising a synchronousdemodulator communicatively coupled between the controller and at leastone of the transducer elements to provide the phase of each derived atleast one signal relative to a phase of a respective signal provided bythe signal source.
 5. The medical system of claim 1 wherein thecontroller performs a frequency domain transform to determine eachrespective set of one or more values.
 6. The medical system of claim 1wherein the controller performs a Fourier transform to determine eachrespective set of one or more values.
 7. The medical system of claim 1wherein each respective input signal comprises a number of alternatingHIGH periods and LOW periods within a predetermined time duration, onepair of adjacent HIGH and LOW periods defining a respective duty cycle.8. The medical system of claim 7 wherein each of at least one of theHIGH periods and the LOW periods of each respective input signalcomprises a plurality of periodic continuous signals.
 9. The medicalsystem of claim 7 wherein each set of one or more response signalscomprises a voltage signal and an electrical current signal, the medicalsystem further comprising an analog-to-digital converter arranged tosample each of the voltage signal and the electrical current signal ineach set of one or more response signals synchronously with thealternating HIGH periods and LOW periods of the respective input signalcorresponding to the set of one or more response signals.
 10. Themedical system of claim 1 wherein each set of one or more responsesignals comprises a voltage signal and an electrical current signal. 11.The medical system of claim 1 wherein the sensing system comprises oneor more resistance temperature detectors, the temperature change atleast proximate to each of the one or more transducer elements sensed bya respective one of the one or more resistance temperature detectors.12. The medical system of claim 1 wherein the structure is selectivelyconfigurable between a delivery configuration in which the structure ispercutaneously deliverable to the intra-cardiac cavity and an expandedconfiguration in which the structure is expanded within theintra-cardiac cavity, the structure sized too large to be deliveredpercutaneously to the intra-cardiac cavity in the expandedconfiguration.
 13. The medical system of claim 12 wherein the one ormore transducer elements comprise a plurality of transducer elements, atleast a first transducer element of the plurality of transducer elementsspaced on the structure from a second transducer element of theplurality of transducer elements such that at least the first transducerelement of the plurality of transducer elements is positioned on aportion of the structure lying across a portion of one of the one ormore ports and the second transducer element of the plurality oftransducer elements is positioned on a portion of the structure whichdoes not overlie the one of the one or more ports.
 14. The medicalsystem of claim 13, further comprising an ablation source coupled totransfer energy to or from the one or more transducer elements.
 15. Themedical system of claim 13, further comprising a radio-frequencygenerator arranged to provide a varying current to at least onetransducer element of the plurality of transducer elements to provideenergy to the tissue wall from the at least one transducer element ofthe plurality of transducer elements.
 16. The medical system of claim 13wherein the controller provides the information in the form of a map ofthe location of at least one of the one or more regions of the interiorsurface of the tissue wall and the location of the at least one of theone or more ports relative to the location of the at least one of theone or more regions of the interior surface of the tissue wall.
 17. Themedical system of claim 13 wherein the controller provides a map of eachdetermined respective set of one or more values.